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June 24, 1930. E. BRAUER ,2

TRANSMISSION OF MESSAGES BY ELEcTR m exETIcwkvhs- Filed new. 9, 1925 Fig.1.

JC 5 4 6 [v 8 M 1 i n lz n j i I 1 I T I v w 2/ Patented June 24, 1930 p -ERNs'r lBRKUER, or vore rsnonr, GER ANY TRAnsMIssmN OEWMESSAGES BY InnEorRo AGNErIo WAVES:

e neatibn meg December 9, 1925, Serial No. 74,414, ana4n 'German y J'anuary 2 5 1924.i

Applications for this invention have been filed in Germa y,;Januar g25, 1924:, and June 25, 1924:. f For the transmission 'of'messages electrio waves the main problem the: separa tion of the message transmitted from other waves which might be stronger. During the transmitting of a simplewave the elirnina tion of disturbances is obtained, and by the constancy of this Wave and thfe da'r n' pi'ng of the antenna together with oscillating-circuits switched onto theQreceiveflfit is possible to practically separate waves,- the lengths of which difier' by some percents. As, however, the range ofthe wavelengths at'd'is posal is limited with regard to the minimum value as well as to the maximum fvalue it follows, that only a limitednumbe of messages canbe sent j's'imultaneously through the space. By improving-the tuning thepossible number of jmessages'j may be'increase'd but this is soonlimited' again'when the success s'ion of the different wave-lengths which carry the different messages becomesjall too close, the tuning of thereceiver must be'so sharp that the diflicultyoffinding mes sage increases to an impossibility. It has, therefore, beenpr0posed to use as carrier for the signals, instead of a simple wave, a wave varying two or more times. such "a modulated wave consists, for instance, of a high frequency of 1,000,000 oscillations, which increase however in onehundre'd thousandth of a second fr01nzero-to a maximum valiie to drop again to zero. The "secondfrequency has in this 'caseja' period of vibrations-of 100,000 per second; The valueofjthe maxi: mum amplitude determines in first instance the signal, In the telegraphic ,si gns this maximum amplitude is either equa'ljfto econstant value, c. 'gla's long as the s'ignlasts, or equal to Zero in the interval between two consecutive signs; In the wireless telephony v thefmaxin um amplitude :verie'e in'suene manner that :it svajlue adapts; itself "to the course of the vibrations of thejhunian speech.

By employing such-a secondvariati'on the number of the possible communicationsis increased from n to armespm Eor 'a'triple 50 wave the number would increase ten It has been found that difliculties arise already at a modulated Wave, e. get two-fol'd'va'ri- 'This invention has for its "object to obviate these'diflicu-lties-insuch a manner that, finder certainconditions, not only atwo-Tol'dbut even a three-fold v'ariationcan be practically employed, It has beenffound, that at the multiple wave telegraphyljor teleph- I on'y) disturbances become prejudicial in-a 51' separating the, waveso'f the same high-free quency,"if the variation frequency is fcliflen ent, fofrinstance a'tthe high frequency 1,000,-

000, to separate intermediate frequencies of 1: 7 80,000 and 100,000. With this object inview the receiver energy i's in fii'st instance sifted bymeans of oscill'ating'circuits which are syntonized to; high frequency in the fexanipl'e given 1,000,000), whereupon'fa' rectification of the current isfj profe liioed which gives an energy oscillating in the variation frequency. This energy acts upon osfcilliating circuits which are *syn'tonized to the fifequency which exists iii the signal; the example 100,000 and eliminate ji'i it eifeiiri frequencies (in the example 8 0,000)" this follows rectification anclvcensequeiiti' reception of the signal which, 'ac'cfordiiig to its "kind, is feither recorded thefMorse 'si: receiver'or rendered audible in th ertelephbne. If'ther'e exists an interfering fie quency of ,fgreat energy ain'd of jt he same oscillation period 1,000,000,jit'w ill ijjirtit b H able to enter fihto thef'ci'r'c'uits tiff intermediate freque'ncy', but, ifit should he "suddenly interrupted, will give toth intermediate frequencycircuits]anliinpu'lse to vibrate and ehere yee'use disturbante, Thi'sfdist'nrbance v is COiKIImESIr in the i r'iiiltipletelegraphy, which 9 0 has hitherto notfbeendisc'o fed, Accordmg to the inventi'oiiit 1's "av t d by the ins'ertron of an element n'iftojthfe circuit which ement will wea en the interfering energy, d

before the sameeah giveijanimpulse to the intermediate frequency circuits, so much that 'this int'erferin'g 'energyis no longer eases tial'ly' strohger than the ener y time signal.

Aconductinlg eflferiientadapted forthi's pureSe'eprefemmy any g'ow cathode 'tube and, under certain conditions, also gas disa charge tubes which possess the property to than the signal energy is, for instance, in-

, serted at its place in the following manner into the receiving apparatus: Upon'the high frequency oscillation circuits and eventually upon an amplifier follows a rectifier which transmits the signal energy as oscillations V valve24 and the phones 27; v a

Even in this arrangement the interfering energy might, under certain conditions, make,

of a wave current. Asa strong interfering energy of equal high frequency would result in the signal repres entin'gjonly comparatively weak fiuctuat1ons of a high current value,,an lntercepting current portion beh nd 7' the rectifier would really neutralize the signal energy. For this reason the wave current is, according to the invention transformed, 'clirectlybehind the rectifier, into an] alternating current, preferably by an aperiodic'inductive transmission. Then follows the device for eliminiating the interfer- Eng energy which cuts off directly, above the amplitude of the signal the interfering en ergy perceivableat this instant only asv cur rent shock and then follow the circuits syn? toni zed to the intermediate frequency."

f Two diagrams of suitablev receiving cir-.

cuits are shown, by way of example, in the 3 accom' an in drawin s.

"Fig. 1 representsa-simple receiving syste'm.v

Fig. 2 represents. a receivingsystem-for greater sensitiveness. v i

j 1 is the receiving anntenna 2', a circuit which is tuned to the wave length; 3, avalve used as detector; and 4 an aperiodic transformer arranged I between the anode circuit 7 of the valve 3 and the grid circuit of a valve whic'hjacts as a limiter and at the same time as an amplifier.-"Thecircuit 6, which is tuned to the amplitude frequency, passes the energy, through'the medium of a transformer 7,, on toa second rectifying valve 8 the anode circuit 10' of which contains the phones 9. A condenser isarranged across the terminals of thelatter.

fVVhen a very pow'erf V .q'uired, ..thearrangement shown in Fig. 2,

which contains six valves, may be resorted tofi'In this case the receiving antenna 11 is connected to earth through a resistance 12 and direct to a high-frequency amplifier 13. The connection between the latter and, another high-frequency amplifier 17., which also acts as a preliminary limiter, 'may contain resistances 14' and 15 and a'condenser 16. In and behind the anode circuitof' the valve 17 the high-frequency tuning circuit 18 is arranged. The transformer 19 passes the'impulses on to the grid of a valve 20 which rectifies the high frequency and produces a wave train whose oscillations are de-V in another manner. g v ,It is not possible to build an oscillating V circuit, especially v an antenna; with such 1 little damping that a normal high frequency wave, the amplitude of which can" for in 1 receiver is reterminedby theamplitude frequency which, 7 7 a as already described, is .a" frequency lyingv between the high frequency and'the signal frequency. An' aperiodic transformer '21 converts the impulses into an alternating current whichpasses through'a limiter-22. The anode of thejlatter is. connected to a cir-' amplifier 26 may be arranged between the,

itself ,perceivable in a, disagreeable manner might occur,"if the damping of the circuits,

. especially of thelhigh frequencycircuitgis 'no't sufliciently strong. This has'really not yet beensufiiciently recognized in. the multiple wave 1 telegraphy, although} similar phen'omena'have been. known for along time in thesimple wave telegraphy, It is true that these phenomena manifest themselves 'and choking of the intermediate frequency stance be, influenced-bythehuman speech,

oscillates through in $110113 degree, and thus chokes the human speech, as such a very great number of high frequency oscillations acts upon. one single oscillation. of speech. In the double-wave telegraphy this is however not at allthe same, as the intermediate 7 frequency is not at allinsignificantly little with regard to the high frequency. In the example given it was ten times less{ hilst,

therefore, in the simple wavetelegraphy, an

oscillating throughand choking of the sig-' nalcan occur only'in specialarrangements' comprising: artificially' reduced I damping (glow cathode tubes with return coupling) the intermediate frequency becomes perceivable already at a damping equal to 1/10, so thatitis necessary to specially take these conditions into consideration. 1 According to the oscillating through and the'choki'ngof a v .1 the invention the damping of the clrcuits is f adapted everytime to the relation of the a high frequency to the intermediate frequency,, or of the: intermediate frequency to the signal frequency. By taking this point into considerationfit ispossible to obtain by rathe'rhighdamping not: only two-fold but i {even three-fold variation ofv the waves and thereby two;fold or. three-fold selectivity.-

Three-fold variation according togthe invention is certainlyalwa-ys possible in the teleg:

raphy. ,The telegraphy frequency can be increased ft'olthevalue of several hundreds per second without the' danger that abnormal'da'mping; should occur and ,through the 7 same evident reduction of the number of. In this case a damping. will be suflicient like that which is found to q practical dampings. 10'

communications.

be practical for other reasons.

The application of the three-fold variation is not only possible for the telegraphy. In the telephony two-fold variation is possible, under all practical conditions, for the In a special field however, especially it short e. g. very high frequency waves are used a three-foldvariation and consequently" an enormous increase of the number of communications will also be possible in the telephone-transmission.

In order to obtain desired damping a resistance can be inserted into the antenna or into the oscillating circuit. The inserted resistance is preferably made variable as in this case the selectivity can be adjusted at any time to the value determinedby the interferences. 7

It is not my intention to limit my invention to the details of the method described above nor to the means shownby way of K example in the accompanying drawings as any practical varlations and modifications falling under the general idea of tion might be applied. 7 V I claim i q A method for the transmission of wireless messages from antennae and for selectively receiving these messages from any one of said antennae consisting in successively modulating lower intermediate frequencies upon a high frequency carrier wave to obtain a multiplicity of messages,' selectively receiving and detecting this successively modulated carrier Wave free from interfering signal Wavesso'that the energies received become almost zero at the zero points of the transmitting waves, by damping the disturbing energies approximately to the amount of the signal amplitude at eachstage of demodulation in advance of the respective my inventuned circuit of lower frequency.

In testimony whereof I afiix my signature.

ERNST BRAUER. 

